Telephone systems

ABSTRACT

A mobile telephone system is provided with a new architecture for dealing with voice internet protocol traffic.  
     Real time traffic from mobile stations ( 22 ) is routed by a public land mobile telephone network internet protocol core ( 20 ) directly to one of two media gateways ( 28,32 ) respectively serving a plain switched telecommunication network/integrated services digital network ( 26 ) and an internet protocol backbone ( 30 ) without passing through the usual general packet radio system (GPRS) specific gateway.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of European Patent ApplicationNo. 00304249.6, which was filed on May, 19, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to telephone networks and, inparticular but not exclusively, telephone networks for mobile telephonesystems.

[0004] 2. Description of the Prior Art

[0005] The structure of telephone networks employing third generationinternet protocol industrial focus group architecture (3G IP) and thirdgeneration partnership project architecture (3G PP) is such that anyvoice internet protocol traffic (VoIP) goes through a fairly lengthyroute within the network. Thus, for example as shown in FIG. 1, VoIPtraffic originating at a mobile station (T₁) 2 and destined for a targetstation (T₂) 14 takes the following route; starting from the mobilestation 2, traffic is passed by a radio network controller (RNC) 4 to aserving GPRS (general packet radio system) support mode SGSN 6. Fromthere the signal is passed by a gateway GPRS support node (GGSN) 8 to amedia gateway (MGW) 12, when a public switch telephone network (PSTN) ismet or when transcoding is required, following which the destination ofthe target telephone (T₂) 14 is reached.

[0006] The traffic handling using the path as outlined above can be veryinefficient.

[0007] So far there is no co-ordination between choice of GGSN and VoIPmedia gateway (MGW). The determination of GGSN (when setting up PDPbearer) and choice of MGW (determined by application level call control)are two independent procedures. However, as the traffic has to passthese two points, the determined GGSN and MGW can result in a less thanoptimum traffic route. For example, this would happen when the mobilestation (MS) GGSN and MGW form a triangle.

[0008] In the public land mobile network (PLMN) (eg the mobile telephoneoperators network) traffic has to pass through a first interface Iu-psbetween the RNC 4 and the SGSN 6, a second interface Gn between the SGSN6 and the GGSN 8. As a result, the user packet acquired the followingprotocol headers or series of codes; real time transport protocol/userdatagrams protocol/internet protocol/GPRS tunnelling protocol/user datagram protocol/internet protocol/L1, 2 (RTP/UDP/IP/GTP/UDP/IP/L1,2). Theresult is that for real time or voice message, the resource usage is low(about 25%).

[0009] It is an object of the present invention to provide an improvednetwork architecture.

SUMMARY OF THE INVENTION

[0010] According to the present invention there is provided a mobileradio system comprising a plurality of mobile stations linked to a radionetwork controller, a first network comprising a public switchedtelephone network and/or an integrated services digital network, asecond network comprising a public internet system, a first real timemedia gateway providing access to and from the first network, a secondreal time media gateway providing access to and from the second network,and a third general packet radio system (GPRS) specific gatewayproviding access to and from the second network, an internet protocolnetwork which responds to the address in the headers of the data streamflowing between the radio network controller and its destination todirect the data stream to its destination through a one of said first,second and third gateways, selected in accordance with the nature of thedata in the data stream whereby real time data is directed througheither said first or said second gateway without passing through saidthird gateway.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A mobile telephone network embodying the present invention, willnow be described, by way of example, with reference to the accompanyingdiagrammatic drawings, in which:

[0012]FIG. 1 is a block diagram of the main components of an existingnetwork;

[0013]FIG. 2 is a block diagram of a network embodying the invention,showing the physical connections between the main components of thenetwork; and

[0014]FIG. 3 is a block diagram illustrating the logical connectionbetween the main components of the network of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] The network shown in FIG. 2 includes a PLMN internet protocol(IP) core or cloud 20. This core 20 is connected to a mobile station 22through a radio network controller (RNC)/radio access network (RAN) 24.The PLMN IP core 20 is coupled to plain switched telecommunicationnetwork (PSTN)/integrated services digital network (ISDN) 26 through atime division multiplexing—real time transport protocol, media gateway(TDM-RTP), MGW 28.

[0016] The PLMN IP core 20 is connected to an internet protocol IPbackbone network 30 by two routes. A first route involves a real timetransport protocol—real time transport protocol media gateway(RTP-RTP-MGW) 32 while the second route involves an SGSN 34, a GGSN 36.A media gateway controller 40 controls the routes.

[0017] It will thus be seen that voice internet protocol traffic can nowreach the IP backbone 30 by incurring less header content.

[0018]FIG. 3 illustrates the logical connections between the componentsshown in FIG. 2 with control connections being shown in broken lines,media connections being shown in a single continuous line and media andcontrol connections being shown in parallel lines, one thick one thin.

[0019] The interfaces between the units are as follows. Gx is theinterface between the RNC 24 and the MGW 28, Gy is the interface betweenthe RNC 24 and the MGW 32. Iu-ps is the interface between the RNC 24 andthe SGSN 34. Gn is the interface between the SGSN 34 and the GGSN 36 andGi is the interface between the GGSN 36 and the IP backbone 30.

[0020] As can be seen, since the MGWs 28 and 32 are connected to the RNC24 through the PLMN IP core 20, any MGW can talk to any RNC within asingle management (mobile operators) domain.

[0021] It will be appreciated that the VoIP flow goes through one of theMGW's 28, 32 which is connected to the PLMN IP core network 20. If thecall traffic is going to the PSTN/ISDN network immediately, a RTP-TDMgateway 28 will be used. Otherwise, if traffic is going to anotherinternet protocol end point which can include an PSTN/ISDN gateway, thenthe RTP-RTP GW 32 should be used. Both types of MGW 28 and 32 canperform transcoding functions.

[0022] The MGW for each VoIP flow will be the anchoring point duringeach communication session. The selected MGW can switch the VoIP flowfrom one RNC 24 to another in the same system under the control of theMGC 40 which itself receives instructions from the SSGN 34 and from theGGSN 36.

[0023] Changes may be made in the combination and arrangement of theelements as herein before set forth in the specification and shown inthe drawings, it being understood that changes may be made in theembodiment disclosed without departing from the spirit and scope of theinvention and defined in the following claims.

1. A mobile radio system comprising a plurality of mobile stationslinked to a radio network controller, a first network comprising a plainswitched telephone network and/or an integrated services digitalnetwork, a second network comprising a public internet system, a firstreal time media gateway providing access to and from the first network,a second real time media gateway providing access to and from the secondnetwork, and a third general packet radio system (GPRS) specific gatewayproviding access to and from the second network, an internet protocolconnection system which responds to the address in the headers of thedata stream flowing between the radio network controller and itsdestination to direct the data stream to its destination through a oneof said first, second and third gateways, selected in accordance withthe nature of the data in the data stream whereby real time data isdirected through either said first or said second gateway withoutpassing through said third gateway.
 2. A system according to claim 1,wherein said first gateway is a time division multiplexing to real timetransport protocol media gateway.
 3. A system according to claim 1,wherein said second gateway is real time transport protocol to real timetransport protocol media gateway.
 4. A system according to claim 1,wherein the first and second gateways comprise a common gateway.
 5. Asystem according to claim 1, wherein the third gateway is a gateway GPRSsupport node (GGSN).
 6. A system according to claim 1, wherein theinternet protocol network comprises a public land mobile telephonenetwork internet protocol core network.
 7. A system according to claim1, wherein the path from the radio network controller to the thirdgateway involves a serving GPRS service node (SGSN).
 8. A systemaccording to claim 7, comprising a media gateway controller forcontrolling said first, second and third gateways and said SGSN.
 9. Asystem according to claim 1, including a call control server forcontrolling calls between said third gate and said second network.